Table Of Content—
March 1992 Letters 41
The nestling hawk was removed from the nest and taken to the Small Animal Veterinary Clinic at Michigan State
University. There it was temporarily cared for and then placed into a local Red-tailed Hawk nest.
The presence of a nestling hawk in a Bald Eagle nest is unexplained, but at least two possible scenarios may apply.
One possibility is brood parasitism by the parent hawks. Although brood parasitism has been documented in five avian
families: Anatidae, Cuculidae, Indicatoridae, Icteridae, and Ploceidae, (J.C. Welty, 1975, The Life of Birds, W.B.
Saunders Co., New York) it has never been recorded in the family Accipitridae.
For brood parasitism to have occurred, a female Red-tailed Hawk had to enter the eagle nest, contend with an adult
Bald Eagle with newly hatched nestlings, and lay its egg. The egg then had to be incubated for approximately 30 days
(F.L. Beeby, 1976, Hawks, Falcons and Falconry, Hancock Home Publisher, Ltd., New York) by either the adult
eagles, the nestlings or both. This scenario is unlikely.
A second explanation is non-lethal predation followed by parental care. One of the adult eagles may have captured
the nestling hawk and failed to kill it during capture and transport. The nestling hawk had a full crop when we
discovered it, suggesting that either the adult eagles had fed it, or that it had recently been transported to the nest and
still had a full crop from its natural parents. Corroborating this is the presence of other raptor species in an analysis
of Bald Eagle prey items collected at nests in the midwest (K.D. Kozie and R.K. Anderson, 1991, Archives of
Environmental Contaminants and Toxicology 20:41-48; W.W. Bowerman IV and J.P. Geisy, Jr., 1991, Ecology of Bald
Eagles on the Au Sable, Manistee, and Muskegon Rivers, Michigan State University, East Lansing, MI). We believe
that this scenario is a more likely explanation than brood parasitism.
Funding for this project was received from Consumers Power Company, Michigan Department ofNatural Resources
EARTHWATCH.
Natural Heritage Program-Nongame Wildlife Fund, U.S.D.A.-Forest Service and Thanks goes
to B.R. Richardson for assisting in the field. P.T. Stapp and L.L. Williams provided helpful comments on an earlier
draft. Assistance was provided by J.A. Sikarskie at Michigan State University-Small Animal Veterinary Medicine.
Patrick R. Stefanek and William W. Bowerman IV, Department of Fisheries and Wildlife, Pesticide Research
Center, Institute for Environmental Toxicology, Michigan State University, East Lansing, MI 48824, U.S.A.;
Teryl G. Grubb, U.S.D.A.-Forest Service, Rocky Mountain Forest and Range Experiment Station, Forestry
Sciences Lab, ASU Campus, Tempe, AZ 85287-1304, U.S.A.; and John B. Holt, Jr., 838 Johnson Street, North
MA
Andover, 45858, U.S.A.
J Raptor Res. 26(1):41 -42
© 1992 The Raptor Research Foundation, Inc.
Talon Grappling by Aplomado Falcons and by Golden Eagles
On 31 January 1979, while observing raptors of seven species along a fire line in central Venezuela, I saw various
chasing and stooping interactions between some of the five Aplomado Falcons Falcofemoralis) present. One of these
(
stoops I fortuitously photographed. A juvenile (by plumage) female (by size) made a long, shallow stoop on an adult
m
(by plumage) male (by size) perched about 20 above the ground in the upper canopy of a tree. The defensive
response of the male was so quick that the episode was little more than a blur to the unaided eye. Fortunately, the
camera (Fig. 1) captured the critical detail. From the photograph and knowledge of the birds’ positionsjust before and
after the incident, it was clear that the male sprang into the air, thrust his feet upward, grasped the female’s foot, and,
impelled by the female’s momentum, whirled at least half a revolution before the birds separated. This may be the
first published account of grappling and whirling for the Aplomado Falcon. It provides detail on the mode of contact
of the birds during the bout, something that is seldom determinable for any species.
The second observation is an extreme example of grappling and whirling for the Golden Eagle (Aquila chrysaetos).
Grappling is common for some eagles (L. Brown and D. Amadon, 1968, Eagles, Hawks and Falcons of the World,
McGraw-Hill Book Go., New York), but rare for the golden (D.H. Ellis, 1979, Wildlife Monographs No. 70; A.R
Harmata, 1982, Raptor Research 16:103-109). On 18 March 1985, I observed three adult Golden Eagles flying along
an elevated cliff rim in southeastern Arizona. The largest bird (presumably a female) was attended by two smaller
H
birds (presumably males) that emphatically stooped at one another. I observed this combat from 1317-1323 when
the two males bound together and whirled at least 19 revolutions before disappearing from view beneath the forest
m
canopy. I estimated that the two fell at least 100 during the bout, but could not determine whether the eagles actually
collided with the ground. The female swooped twice above the combatants on the ground, then drifted away from the
)
42 Letters Vol. 26, No. 1
Figure 1. Aplomado Falcons grappling and whirling. Adult male (above) was perched in treetop when juvenile
female stooped from left.
area. After 1 1 min, first one male, and then the second, flew from the touch down zone and rejoined the female. The
A Hawk
trio then drifted north out of sight with the males again stooping at each other. Red-tailed Buteojamaicensis
( )
was present, soaring above and occasionally stooping at the trio, during almost the entire episode. This may be the
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most extended grappling and whirling bout ever reported, at least for the Golden Eagle. David H. Ellis, U.S. Fish
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and Wildlife Service, Patuxent Wildlife Research Center, Laurel, 20708.
Raptor Res. 26(l):42-43
J.
© 1992 The Raptor Research Foundation, Inc.
A Previously Undescribed Falcon Flight Display
It is something of a surprise for a social display to suddenly be discovered in a supposedly well-studied species. An
example is the recent description of the Bowing display for the Cooper’s Hawk Accipiter cooperii (R.N. Rosenfield
(
and J. Bielefeldt, 1991, Condor 93:191-193). The Prairie Falcon (Falco mexicanus) and Peregrine Falcon (Falco
peregrinus) have also received great attention during the last three decades, yet I am unaware of any published account
of a “deep-flap” display I will next describe.
In 1981, at three different cliffs, all in Arizona, I observed a flight display that was distinctly different from normal
flapping flight. On 11 February at 1607 H, at a site on the Tohono O’Odham Indian Reservation, an adult Prairie
Falcon (probably a male by size comparison with the other falcon attending the cliff) stooped upon and flushed a Red-
